Retarget with FB ads, with free offer

Hey

I'm looking to do some retargeting with FB ads for the people that visited my site but didnt convert. Is there a (not too painful) way to offer them a unique coupon code or free offer somehow? I only want the specific retrageted people to be able to use it and not be abused.

Thanks

Have you installed pixel in your site?is yes,then you can create custom audience based on people that visit your site.